Scientists are trying to find out why Anchovies in the Bay of Biscay are shrinkingIt is a fact that can be seen from year to year. The AZTI technology center, which specializes in marine and food research, revealed the extent to which the size of anchovies in Bizkaia Bay has decreased in the period from 1990 to 2021.
Study published in the journal Global Change Biologyscientists have confirmed something visible reduction in height and average weight Adult individuals of the European anchovy or anchovy (Engraulis encrasicolus). The analysis shows that the samples are now not only smaller but also have a slimmer shape.
“The reduction in weight is slightly more pronounced than the reduction in overall length; the reduction rates are “They have accelerated by up to 25% per decade in the last two decades.”points out Fernando Taboada, one of the main authors of the AZTI study.
Reasons for decrease
So what is the reason for this situation? Although these changes are partly related to ocean warming, researchers involved in the study suggest there is a complex interplay of environmental factors but ignore that fishing pressure is making a significant impact.
“We found that samples were smaller due to the abundance of anchovies, but that this relationship with population density was less pronounced at later stages. It turns out that the main reason for the decrease in size is temperature” adds Guillem Chust, one of the study’s scientific authors.
“In general, the growth of juvenile fish living in warm waters is faster than their counterparts living in cold waters; But these conditions Higher temperatures slow further developmentExperts explain that this results in a smaller adult body size, known as the temperature size rule (TSR).
larger in cold waters
The researchers confirmed two ecogeographic hypotheses to explain how the size of fish changes when water temperature changes: The first states that when comparing different species of fish that are closely related to each other (for example, species of the genus): engraulis), generally fish tend to be larger in colder waters.
The second hypothesis focuses on different populations of the same species. The team’s observations reveal that, in general, individuals from different anchovy populations in Europe tend to be larger in cold seas.
However, as AZTI notes, “It is very important to be careful as the study is based on observations and has its limitations. “However, there is additional evidence to suggest that the reduction in anchovy size may be an indicator of the response to climate changes and the functioning of the Bizkaia Bay ecosystem.”
Reference work: https://onlinelibrary.wiley.com/doi/10.1111/gcb.17047
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